1. Field of the Invention
The invention relates to electronic data storage and access. More particularly, the invention relates to a method and apparatus for storing and retrieving multiple electronic data streams having different bit rates.
2. Description of the Background Art
Multimedia systems store and retrieve video, audio and other content from mass storage devices, e.g., disk drive arrays. One such system provides video-on-demand (VOD) to an end user. Such a VOD system stores video content in memory and retrieves the content upon demand. The VOD system then serves the video content to the end user requesting the video content.
The VOD system uses a VOD server for storing and accessing video content or a plurality of video files. The VOD server processes the video content as data packets and stores the video content into extents or logical memory blocks within a memory. The data packets generally comply with one or more of the Moving Pictures Experts Group (MPEG) standards. To store these data packets in a redundant manner, the VOD server may stripe the video content over an array of disks within the memory. Each video file may occupy several physical disk blocks or disk tracks within the disk drives.
Multimedia programs are encoded using various resolutions of encoding depending upon the content of the program, i.e., sporting events are encoded with higher resolution than situation comedies. The bit rate of high-resolution encoded program is greater than a bit rate of a low-resolution encoded program. As such, for a given unit of program time, a high resolution encoded program generates more packets than are generated when forming a low resolution encoded program. Consequently, a video server must be able to store a plurality of programs having constant bit rates. To facilitate storage of multiple constant bit rate programs, current servers require the bit rates of various programs to be integer multiple of one another such that the extents of any given program are of equal size and the extents across programs are integer multiples of each other. Such a restrictive storage system is not flexible in providing storage of any form of programming, i.e., programs having non-integer bit rates. Consequently, current video servers do not store programming in an optimal manner.
Therefore, there is a need in the art for an improved method and apparatus for storing an accessing multiple constant bit rate video programs wherein the bit rate of programming can be arbitrary.